Near Field Communication (NFC) is a wireless connectivity technology which allows communication over a short distance between electronic devices, such as, for example contactless smart chips and readers. NFC technology may be particularly suitable for connecting any type of user device and allows fast and easy communications.
Among the protocols usable in NFC technology there are the type A and type B protocols defined in the ISD-14 443 standard. In NFC technology, the transmission of information generally takes place in the form of frames, as is the case, for example, in the type A protocol of the ISO-14 443 standard.
The exchanged frames comprise data bits and parity bits. Conventionally, on transmission the parity bits are calculated by the transceiver head, from the data bits which actually have to be transmitted on the transmission channel and using a predetermined calculation rule, which is generally specific to the communications standard used. On reception, the received parity bits are checked by the transceiver head by carrying out a calculation of these parity bits from the received data bits using the calculation rule, and then a comparison of these calculated parity bits with the parity bits extracted from the received frames.
There are, moreover, communication protocols also using transmission frames, but within which the data bits are encrypted. Moreover, the parity bits are calculated not from the encrypted data bits which will actually be transmitted but from the non-encrypted data bits, and then these parity bits thus calculated are then encrypted.
Despite this specific calculation and this encryption of the parity bits, some of these protocols remain compatible with the ISO-14 443 standard, notably at the level of the structure of the transmission frames. This is the case, for example, for the communications protocol known by its registered trade name MIFARE®. Information on this protocol is disclosed in the document published by the NXP Semiconductors company entitled “AN 10833, MIFARE type identification procedure” rev 3.2, 29 Aug. 2011, 018432. Other details about this protocol are provided, for example, in the document by Michael Silbermann entitled “Security Analysis of Contactless Payment Systems in Practice”, 2 Nov. 2009, Ruhr-Universität Bochum.
The use of such encrypted transmission protocols is incompatible with the use of conventional transceiver heads notably because of the specific calculation and encryption of the parity bits. It is therefore necessary to develop specific transceiver heads incorporating the encryption/decryption algorithm, and the calculation and checking of the parity bits specific to such transmission protocols.
Moreover, the digital information to be transmitted is typically generated by a host microcontroller, and transmitted in plaintext on a bus to the transceiver head, which represents a weak point with regard to security.